A method for preparing resistant starch

Abstract

A method for preparing resistant starch belongs to the field of starch processing. The present invention increases the amylose content by debranching waxy rice starch, reduces the starch molecular weight distribution by ethanol precipitation, and on this basis, utilizes temperature method to drive the formation of type VII starch polyphenol inclusion compound, so as to prepare resistant starch. The main steps include: waxy rice starch gelatinization, pullulanase debranching, adding ethanol precipitation to the debranched starch solution to remove incomplete debranching starch to reduce the starch molecular weight distribution, adding polyphenols, high-speed dispersion 8~10min, cooling to room temperature, standing, centrifugation to obtain starch polyphenol inclusion compound precipitation, washing with anhydrous ethanol to remove free polyphenols on the precipitation surface, drying at 50 DEG C for 10min, i.e., obtaining a highly resistant starch polyphenol inclusion compound, with the advantages of high resistant starch content and high thermal stability.

Description

Technical Field

[0001] The invention discloses a method for preparing resistant starch, which relates to a starch and polyphenol complexation technology and belongs to the field of starch deep processing. Background Art

[0002] Starch and polyphenols can form starch-polyphenol inclusion complexes, which have a structure similar to starch-lipid inclusion complexes. Starch-polyphenol inclusion complexes are also resistant and are therefore considered to be a fifth type of resistant starch similar to starch-lipid inclusion complexes. The applicant has discovered that the resistance of starch-polyphenol inclusion complexes comes from the inhibitory effect of polyphenols on amylase and the single helical structure of starch in the inclusion complex. Therefore, in theory, the resistance of starch-polyphenol inclusion complexes is stronger than that of starch-lipid inclusion complexes. Figure 1 As shown, the inclusion complex formed by starch and guest molecules may form a disordered, loose Type VI crystal inclusion complex with a low degree of crystallinity, characterized by a flat diffraction peak and a low dissociation peak temperature. Alternatively, the inclusion complex may further order to form a strongly crystalline Type VII inclusion complex, characterized by a more perfect crystal arrangement, a sharp diffraction peak, and a higher dissociation peak temperature. Clearly, the Type VII inclusion complex exhibits higher resistance and stability than the Type VI inclusion complex. This suggests that constructing a Type VII starch-polyphenol inclusion complex is beneficial for increasing the resistant starch content and thermal stability of resistant starch.

[0003] Applicants have discovered that increasing amylose content and reducing starch molecular weight distribution can promote the formation of type VII starch-polyphenol inclusion complexes, resulting in strong resistance and excellent thermal stability. Based on this, the present invention debranches waxy starch and uses ethanol precipitation to reduce the starch molecular weight distribution. On this basis, a temperature-driven method is used to prepare starch-polyphenol inclusion complexes, thereby achieving the preparation of resistant starch. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing resistant starch, thereby increasing the added value of starch.

[0005] The technical solution of the present invention is to use waxy rice starch as raw material, enzymatically debranch to increase the amylose content, ethanol precipitation to reduce the starch molecular weight distribution, and temperature-driven method to prepare type VII starch-polyphenol inclusion complex. The process of the present invention specifically includes the following steps.

[0006] (1) Debranching of starch: Waxy rice starch was dispersed in pH 5.5 buffer to a starch concentration of 10.0%, and heated in a boiling water bath for 30 min to completely gelatinize the starch. The starch was cooled to 55 °C, and pullulanase was added at a ratio of 50 U / g starch and reacted for 2 h.

[0007] (2) Ethanol precipitation to reduce the molecular weight distribution of starch: Ethanol was added to the debranched starch solution at a rate of 5 mL / min, accounting for 30% of the volume of the starch solution. This inactivated the enzyme and caused some starch to precipitate, thereby reducing the molecular weight distribution of starch. The solution was allowed to stand for 10 min and centrifuged to obtain the supernatant, which was maintained at 55°C.

[0008] (3) Preparation of starch-polyphenol inclusion complex: Weigh polyphenols at a ratio of 5.0% by weight of starch and dissolve them in a small amount of ethanol. Then add the polyphenol solution to the above supernatant and stir at 17,000 rpm for 8-10 min using a disperser. Cool to room temperature, let stand for 10 min, and centrifuge to obtain a starch-polyphenol inclusion complex precipitate. Wash the precipitate with anhydrous ethanol to remove uncomplexed polyphenols, and dry at 50°C for 10 min to obtain the starch-polyphenol inclusion complex.

[0009] (4) Determination of the digestibility of starch-polyphenol inclusion complex: The resistant starch content of starch-polyphenol inclusion complex was determined using an in vitro simulation method.

[0010] The polyphenol is genistein, quercetin, naringin, gallic acid, ferulic acid or caffeic acid.

[0011] Compared with the prior art, the resistant starch product of the present invention has the beneficial effects of high resistant starch content, good thermal stability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the structure of starch-guest molecule inclusion complex in the background art

[0013] Figure 2 (A) X-ray diffraction pattern and (B) differential thermal scanning pattern of the starch-ferulic acid inclusion complex in Example 1: a is the starch-ferulic acid inclusion complex formed in the control group, b is the starch-ferulic acid inclusion complex prepared by the present invention DETAILED DESCRIPTION

[0014] Example 1

[0015] 10.0 g of waxy rice starch was dispersed in 100 mL of pH 5.5 acetate buffer, and the starch was completely gelatinized in a boiling water bath for 30 minutes. The starch was cooled to 55°C, 500 U of pullulanase was added, and the reaction was allowed to proceed for 2 hours. 30 mL of ethanol was added to 100 mL of the above solution at a rate of 5 mL / min, the mixture was allowed to stand for 10 minutes, and the supernatant was obtained by centrifugation, which was maintained at 55°C. 0.5 g of ferulic acid was dissolved in 2 mL of ethanol, the ferulic acid solution was added to the supernatant, and the mixture was stirred at 17,000 rpm for 10 minutes using a disperser. The mixture was cooled to room temperature, allowed to stand for 10 minutes, and centrifuged to obtain a starch-ferulic acid inclusion complex precipitate. The precipitate was washed with anhydrous ethanol to remove uncomplexed ferulic acid, and dried at 50°C for 10 minutes to obtain a starch-ferulic acid inclusion complex. In order to demonstrate the beneficial effects of the present invention, a temperature-driven method was used to prepare a starch-ferulic acid inclusion complex using debranched waxy rice starch as raw material under the same conditions as above. The structures of the two inclusion complexes were analyzed by X-ray diffractometer and differential calorimetry, and their digestibility was determined by in vitro simulation. Figure 2 As shown in FIG, the diffraction peak of the starch-ferulic acid inclusion complex formed in the control group is broad and smooth, while the peak of the starch-ferulic acid inclusion complex prepared by the present invention is narrow and sharp; the peak dissociation temperature of the starch-ferulic acid inclusion complex formed in the control group is 104.1 o C, the peak dissociation temperature of the starch-ferulic acid inclusion complex prepared by the present invention is 110.6 o C. This indicates that the starch-ferulic acid inclusion complex formed in the control group is a Type VI inclusion complex, while the starch-ferulic acid inclusion complex prepared in the present invention is a Type VII inclusion complex. Accordingly, the resistant starch content in the starch-ferulic acid inclusion complex formed in the control group is 68.87%, while the resistant starch content in the starch-ferulic acid inclusion complex prepared in the present invention is 78.21%. This indicates that the resistant starch product of the present invention has advantages such as strong resistance and high thermal stability.

[0016] Example 2

[0017] 10.0 g of waxy rice starch was dispersed in 100 mL of pH 5.5 acetate buffer, and the starch was completely gelatinized in a boiling water bath for 30 min. The starch was cooled to 55°C, 500 U of pullulanase was added, and the reaction was carried out for 2 h. 30 mL of ethanol was added to 100 mL of the above solution at a rate of 5 mL / min, the mixture was allowed to stand for 10 min, and the supernatant was obtained by centrifugation, and the temperature was maintained at 55°C. 0.5 g of genistein was weighed and dissolved in 2 mL of ethanol. The genistein solution was added to the supernatant, and the mixture was stirred at 17,000 rpm for 10 min using a disperser. The mixture was cooled to room temperature, allowed to stand for 10 min, and centrifuged to obtain a starch-genistein inclusion complex precipitate. The precipitate was washed with anhydrous ethanol to remove uncomplexed genistein, and dried at 50°C for 10 min to obtain a type VII starch-genistein inclusion complex with a resistant starch content of 81.37% and a dissociation temperature of 114.5°C.

[0018] Example 3

[0019] 10.0 g of waxy rice starch was dispersed in 100 mL of pH 5.5 acetate buffer, and the starch was completely gelatinized in a boiling water bath for 30 min. The mixture was cooled to 55°C, 500 U of pullulanase was added, and the reaction was carried out for 2 h. 30 mL of ethanol was added to 100 mL of the above solution at a rate of 5 mL / min, the mixture was allowed to stand for 10 min, and the supernatant was obtained by centrifugation, and the temperature was maintained at 55°C. 0.5 g of quercetin was dissolved in 2 mL of ethanol, the quercetin solution was added to the supernatant, and the mixture was stirred at 17,000 rpm for 10 min using a disperser. The mixture was cooled to room temperature, allowed to stand for 10 min, and centrifuged to obtain a starch-quercetin inclusion complex precipitate. The precipitate was washed with anhydrous ethanol to remove uncomplexed quercetin, and dried at 50°C for 10 min to obtain a type VII starch-quercetin inclusion complex with a resistant starch content of 86.87% and a dissociation temperature of 116.8°C.

Claims

1. A method for preparing resistant starch, comprising debranching waxy rice starch, reducing the molecular weight of starch by ethanol precipitation, and preparing starch-polyphenol inclusion complex by temperature-driven method, characterized in that The ethanol precipitation method was used to reduce the molecular weight distribution of starch and promote the formation of type VII starch-polyphenol inclusion complex. The specific steps were as follows: waxy rice starch was dispersed in pH 5.5 buffer to make the starch concentration 10.0%, heated to completely gelatinize the starch, cooled to 55 ° C, and heated at 50 ° C. Pullulanase was added at a ratio of 100 μg / g starch to react for 2 hours to debranch the starch. Ethanol was added to the debranched starch solution at a rate of 5 mL / min at a ratio of 30% by volume of the starch solution to inactivate the enzyme and precipitate part of the starch, thereby narrowing the molecular weight distribution of the starch. The solution was allowed to stand for 10 minutes and centrifuged to obtain a supernatant, which was maintained at 55°C. Polyphenols were weighed at a ratio of 5.0% by mass of the starch and dissolved in ethanol. The polyphenol solution was added to the supernatant, stirred at 17,000 rpm for 8-10 minutes using a disperser, cooled to room temperature, allowed to stand for 10 minutes, and centrifuged to obtain a starch-polyphenol inclusion complex precipitate. The precipitate was washed with anhydrous ethanol to remove uncomplexed polyphenols, and dried at 50°C for 10 minutes to obtain a starch-polyphenol inclusion complex. The polyphenols were genistein, quercetin, naringin, gallic acid, ferulic acid, or caffeic acid.

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